The invention relates to (1) an optical device for pattern reproduction that combines a coherent light source with a spatial light modulator, and (2) an optical processing system that incorporates this optical device.
The prior art technology is explained by relenting to pattern scribing technology that utilizes light.
Prior art pattern scribing devices (laser scribing devices) that utilize light used methods that are generally divided into the following two methods.
(1) Laser beam scanning method
(2) Mask method
In method (1), scribing was performed on the material by scanning the laser beam two dimensionally according to a pattern using a galvanomirror or a polygon mirror (Japanese Laid-Open Patent Publication 56-118860).
In method (2), scribing was performed by irradiating a laser beam on a mask on which the pattern to be scribed was formed as openings and by projecting the pattern reduced on the material via an imaging lens. Initially, metal plates on which the openings were formed were used as the mask medium. However, due to the cost and trouble of producing the mask, liquid crystal spatial light modulators have received attention in recent years for use as variable masks.
In the method that uses a liquid crystal spatial light modulator as a variable mask, the two-dimensional optical switching effect of the liquid crystal spatial light modulator is utilized to record the pattern as is as a density. FIG. 20 shows a prior art laser scribing device. The light emitted from a laser source 2001 illuminates a twisted nematic (TN)-mode liquid crystal spatial light modulator 2004 on which the density mask of the pattern has been recorded. The transmitted light is converged by a lens 2005 to image the pattern on the surface of a material 106. Those parts of the material surface on which the pattern is imaged are evaporated by the heat of the laser, whereby the pattern is scribed. A (1) TN (twisted nematic)-mode (Japanese Laid-Open Patent Publications 60-174671, 1-176563, 1-176564 and 1-216851) or (2) scattering-mode (Japanese Laid-Open Patent Publications 1-1577912 and 3-18491) is used as the liquid crystal spatial light modulator.
In addition to these, there have been applications of the laser scribing devices that use a liquid crystal spatial light modulator as an open mask. Those that have been searched so far are listed below.
Japanese Laid-Open Patent Publications 62-127710 and 1-257821
U.S. Pat. Nos. 4,586,053, 4,734,558, 4,818,835 and 4,937,424
However, since prior art laser scribing devices used the variable pattern displayed on the liquid crystal spatial light modulator as a mask, their light utilization efficiency was low. Therefore, when the pattern to be scribed had a small total surface area such as that of short character strings or line images, a high-output laser source (or light excitation source) was required, which markedly lowered production efficiency. Also, in order to scribe a pattern on a curved surface, it was necessary to move the lens, mirror and other optical elements at high speed in the direction of depth, thus greatly complicating the device configtrration.
The invention is intended to solve these problems. The invention (1) offers an optical device with high light utilization efficiency that is capable of scribing patterns on curved surfaces by a simple means, (2) offers an optical device with high light utilization efficiency that is capable of three-dimensional formation on curved surfaces, and (3) offers a widely applicable optical processing system that incorporates these devices on robots.